1. Field of the Invention
The present invention relates to a power supply apparatus including a charge-pump type step-up circuit and a regulator for regulating the output voltage of the charge-pump type step-up circuit.
2. Description of the Related Art
A typical power supply apparatus suitably used in a driver for driving a display panel such as a liquid crystal display (LCD) panel of a mobile phone or a personal digital assistant (PDA) includes a charge-pump type step-up circuit and a regulator for regulating the output voltage of the charge-pump type step-up circuit.
A prior art power supply apparatus is constructed by a charge-pump type step-up circuit having a single discharging (step-up) time constant of a smoothing capacitor, and a regulator formed by a voltage divider for dividing the output voltage of the step-up circuit to generate a divided voltage, a comparator for comparing the divided voltage with a reference voltage to generate a comparison output signal, and an AND circuit for supplying a clock signal to the step-up circuit in accordance with the comparison output signal (see: JP-2005-20971A). This will be explained later in detail.